U.S. patent number 4,962,891 [Application Number 07/280,775] was granted by the patent office on 1990-10-16 for apparatus for removing small particles from a substrate.
This patent grant is currently assigned to The BOC Group, Inc.. Invention is credited to Lawrence M. Layden.
United States Patent |
4,962,891 |
Layden |
October 16, 1990 |
**Please see images for:
( Certificate of Correction ) ** |
Apparatus for removing small particles from a substrate
Abstract
Apparatus for removing small particles from a substrate
including superimposed plates forming at least two parallel
chambers and a film-like member interposed between the plates and
adapted to provide flow communication between the chambers to
enable fluid carbon dioxide to form a mixture of solid particles
and gaseous carbon dioxide which flows out of an ejection port
toward the substrate.
Inventors: |
Layden; Lawrence M. (Stanton,
NJ) |
Assignee: |
The BOC Group, Inc. (New
Providence, NJ)
|
Family
ID: |
23074588 |
Appl.
No.: |
07/280,775 |
Filed: |
December 6, 1988 |
Current U.S.
Class: |
239/597; 134/93;
239/590; 451/39; 134/198 |
Current CPC
Class: |
B05B
1/044 (20130101); C01B 32/55 (20170801); B24C
1/003 (20130101); H01L 21/67028 (20130101) |
Current International
Class: |
B24C
1/00 (20060101); B05B 1/04 (20060101); B05B
1/02 (20060101); H01L 21/00 (20060101); C01B
31/22 (20060101); C01B 31/00 (20060101); B05B
001/00 () |
Field of
Search: |
;134/93,182,198,199
;51/320,439 ;239/552,553.3,553.5,555,590,590.5,568,597 ;62/74 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kashnikow; Andres
Assistant Examiner: Trainor; Christopher G.
Attorney, Agent or Firm: Pearlman; Robert I. Nemetz; Carol
A. Rosenblum; David M.
Claims
What is claimed is:
1. Apparatus for removing small particles from a substrate
comprising:
(a) a source of fluid carbon dioxide under pressure and having an
enthalpy below about 135 BTU per pound based on an enthalpy of 0 at
150 psia for a saturated liquid, so that a solid fraction will form
upon the expansion of the fluid carbon dioxide to the ambient
pressure of the substrate;
(b) a nozzle having a first opening for receiving the fluid carbon
dioxide from the source and a second opening for emitting a mixture
of solid and gaseous carbon dioxide toward the substrate, said
nozzle further comprising, said
(1) a pair of plates adapted to be superimposed over each other
collectively defining a first chamber connected to the first
opening and a second chamber spaced apart from the first
chamber;
(2) a foil-like member interposed between the superimposed plates
comprising a hole aligned with the first opening for providing a
pathway for the flow of fluid into the first chamber, and at least
two finger-like projections extending from the first chamber to the
second chamber and together with the superimposed plates forming at
least one first channel providing flow communication between the
first and second chambers, wherein the at least one first channel
is sized to form a restriction such that the fluid forms a first
mixture of gaseous carbon dioxide and fine droplets of liquid
carbon dioxide in the at least one first channel and wherein the
first mixture is converted in the second chamber to a second
mixture containing gaseous carbon dioxide and large liquid droplets
of carbon dioxide; and
(3) a second channel extending from the second chamber to the
second opening enabling the second mixture to expand into said
mixture of solid and gaseous carbon dioxide and exit out of the
second opening toward the substrate.
2. The apparatus of claim 1 wherein the second chamber comprises
substantially parallel superimposed transverse grooves extending
along a substantial width of the plates.
3. The apparatus of claim 2 wherein the first chamber comprises a
transverse groove on one plate and a flat surface portion of the
other plate superimposed over said transverse groove.
4. The apparatus of claim 2 wherein the first chamber comprises
substantially parallel superimposed transverse grooves extending
along a substantial width of the plates.
5. The apparatus of claim 2 wherein the length of the second
chamber is about equal to the width of the second opening.
6. The apparatus of claim 1 wherein the sum of the widths of the
first channels is at least about 10% of the width of the second
opening.
7. The apparatus of claim 6 wherein the sum of the widths of the
first channels is from about 10 to 20% of the width of the second
opening.
8. The apparatus of claim 1 comprising a plurality of first
channels.
9. The apparatus of claim 1 wherein the second opening comprises
divergently tapered walls having an angle of divergence of up to
15.degree..
10. The apparatus of claim 2 wherein the angle of divergence is
about 4.degree. to 8.degree..
11. The apparatus of claim 1 wherein the width of the foil-like
member is at least about 0.001 inch.
12. The apparatus of claim 11 wherein the width of the foil-like
member is from about 0.001" to 0.020 inch.
13. The apparatus of claim 1 further comprising means for
maintaining the pressure in the second chamber from about 80 to 160
psia.
14. The apparatus of claim 1 further comprising means for
maintaining said plates in said superimposed position.
15. Apparatus for removing small particles from a substrate
comprising:
(a) a source of fluid carbon dioxide under pressure and having an
enthalpy of below about 135 BTU per pound based on an enthalpy of
zero at 150 psia for a saturated liquid, so that a solid fraction
will form upon the expansion of the fluid carbon dioxide to the
ambient pressure of the substrate;
(b) a nozzle having a first opening for receiving the fluid carbon
dioxide from the source and a second opening having tapered walls
diverging at an angle of up to 15.degree. for emitting a mixture of
solid and gaseous carbon dioxide toward the substrate, said nozzle
further comprising,
(1) a pair of plates adapted to be superimposed over each other
collectively defining a first chamber connected to the first
opening and having complimentary transverse grooves which when
superimposed define a second chamber spaced apart from the first
chamber, said first and second chambers having a length of from 20
to 60% of the overall width of the plates;
(2) a foil-like member interposed between the superimposed plates
and comprising a hole aligned with the first opening for providing
a pathway for the flow of said fluid into the first chamber, and at
least three finger-like projections extending from the first
chamber to the second chamber and together with the superimposed
plates forming at least two first channels having a combined width
of the second opening and providing flow communication between the
first and second chambers, wherein each of the at least two first
channels are sized to form a restriction such that the fluid forms
a first mixture of gaseous carbon dioxide and fine droplets of
liquid carbon dioxide in the at least two first channels and
wherein the first mixture is converted in the second chamber to a
second mixture containing gaseous carbon dioxide and larger liquid
droplets of carbon dioxide; and
(3) a second channel extending from the second chamber to the
second opening enabling the second mixture to expand into said
mixture of solid and gaseous carbon dioxide and exit out of the
second opening toward the substrate.
16. The apparatus of claim 15 wherein the sum of the widths of the
first channels is from about 10 to 20% of the width of the second
opening.
17. The apparatus of claim 15 wherein the second opening comprises
divergently tapered walls having an angle of divergence of 4 to
8.degree..
18. The apparatus of claim 15 wherein the thickness of the
foil-like member is at least 0.001 inch.
19. The apparatus of claim 15 further comprising means for
maintaining the pressure in the second chamber from about 80 to 160
psia.
20. The apparatus of claim 15 further comprising means for
maintaining said plates in said superimposed position.
Description
The present invention is directed to apparatus for removing minute
particles from a substrate employing a stream containing solid and
gaseous carbon dioxide.
BACKGROUND OF THE INVENTION
The Assignee of the present application has a pending application,
U.S. Patent Application Ser. No. 116,194 filed on Nov. 3, 1987
which is a continuation-in-part application of U.S. Pat.
Application Ser. No. 041,169, filed Apr. 22, 1987 which describes
apparatus and methods for removing finely particulate surface
contaminants from a substrate such as a semiconductor wafer.
The apparatus, as shown in particular in the drawings, provides for
the flow of fluid carbon dioxide into a chamber wherein the fluid
is converted to a mixture of gaseous carbon dioxide and fine
droplets of carbon dioxide. This mixture is then transported in
metered amounts through the use of e.g. needle valve or a
restricted orifice to a coalescing chamber where the fine droplets
are converted to larger droplets to form a second mixture. The
larger droplets are then formed into solid particles as the feed
passes from the coalescing chamber through a tubular passageway
into a second orifice and out of an exit port. The entire
disclosure of U.S. Ser. No. 116,194 is incorporated herein by
reference.
The apparatus of the present invention represents an improvement
over the apparatus described above in that it is easier to
manufacture, provides a more reliable means for metering the
mixture and provides for more even distribution of the mixture,
especially as it flows into the coalescing chamber. Another benefit
of the present invention is that the solid product stream is
directed out of the exit port and onto the substrate to provide
more uniform cleaning. Cleaning is enhanced by employing an
ejection port which has a slit-like shape and may be made of any
desired width. The larger the width, the greater the cleaning area
per pass.
In accordance with this invention there is provided a novel
apparatus for removing small particles from a substrate which
provides more effective means of controlling the flow rate of the
fluid mixtures and thereby provide a more effective means of
removing contaminants from a substrate surface.
SUMMARY OF THE INVENTION
The present invention is generally directed to an apparatus for
removing small particles from a substrate comprising:
(a) a source of fluid carbon dioxide under pressure and having an
enthalpy of below about 135 BTU per pound based on an enthalpy of
zero at 150 psia for a saturated liquid, so that a solid fraction
will form upon the expansion of the fluid carbon dioxide to the
ambient pressure of the substrate;
(b) a nozzle having a first opening for receiving the fluid carbon
dioxide from the source and a second opening for emitting a mixture
of solid and gaseous carbon dioxide toward the substrate, said
nozzle further comprising,
(1) a pair of plates adapted to be superimposed over each other
collectively defining a first chamber connected to the first
opening and a second chamber spaced apart from the first
chamber,
(2) a foil-like member interposed between the superimposed plates
and comprising a hole aligned with the first opening for providing
a pathway for the flow of said fluid into the first chamber, and
fine droplets of liquid carbon dioxide, and at least two
finger-like projections extending from the first chamber to the
second chamber and together with the superimposed plates forming at
least one first channel providing flow communication between the
fluid forms a first mixture of gaseous carbon dioxide and fine
droplets of liquid carbon dioxide in the at least one first channel
and wherein the first and second chambers, wherein the first
mixture is converted to a second mixture in the second chamber
containing gaseous carbon dioxide and larger liquid droplets of
carbon dioxide, and
(3) a second channel formed by said plates and extending from the
second chamber to the second opening enabling the second mixture to
expand into said mixture of solid and gaseous carbon dioxide and
exit out of the second opening toward the substrate.
More specifically, the present invention employs a thin foil
between superimposed plates where the channels formed by the foil
in conjunction with the plate surfaces provide a stationary means
of metering the flow of carbon dioxide from the first chamber to
the second or coalescing chamber. There is also provided a flat
widened pathway formed by the superimposed plates for transporting
the mixture from the coalescing chamber to the exit port which
provides a move uniform flow of product toward the substrate and
constitutes a second restricting orifice to maintain the desired
pressure in the coalescing chamber.
The following drawings and the embodiments described therein in
which like reference characters indicate like parts are
illustrative of the present invention and are not meant to limit
the scope of the invention as set forth in the claims forming part
of the application.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the apparatus of the present
invention with the superimposable plates operatively secured to
each other;
FIG. 2 is a side view with a partial cross-section of the device
shown in FIG. 1 showing the plates secured to each other;
FIG. 3 is a front view of the device shown in FIG. 1 showing the
exit port;
FIG. 4 is a perspective view of the embodiment shown in FIG. 1
showing the film-like member in position between the plates;
FIG. 5A is a plan view of the plates laid open showing the
positioning of the film-like member on the bottom plate with the
top plate having a single transverse groove;
FIG. 5B is a plan view of the laid open plates similar to FIG. 5A
with the top plate having two transverse grooves;
FIG. 6 is a partial side view taken along line 6--6 of FIG. 1;
and
FIG. 7 is an elevational view of another embodiment of the
invention showing a fluid receiving reservoir in the middle of the
first chamber.
DESCRIPTION OF THE INVENTION
Referring to the drawings, and specifically to FIGS. 1-5B the
apparatus 2 of the present invention includes a fluid carbon
dioxide receiving assembly 4 which is connected to a fluid carbon
dioxide storage facility (not shown) via connecting means 6. The
connecting means 6 may be a steel reinforced Teflon hose or any
other suitable connecting means which enables the fluid carbon
dioxide to flow from the source to the receiving assembly 4.
The receiving assembly 4 includes a housing 8 having a hole 10
extending through the housing 8. The assembly 4 is either
permanently or removably secured to the apparatus 2 such as by
thread and groove engagement.
The apparatus 2 also includes a pair of plates 12, 14 which are of
complimentary shape and superimposable one over the other. As shown
best in FIGS. 2 and 3, the plates 12 and 14 may be secured to each
other by a plurality of evenly distributed screws 16 which are
insertable into respective holes 18 and 20 or other suitable
securing means.
As best shown in FIGS. 4 and 5A, one embodiment of the invention
provides a transverse groove 28 on the bottom surface 13 of the top
plate 12 extending along a substantial width of the top plate. The
top surface 15 of the bottom plate 14 is provided with a
complimentary transverse groove 30 of like dimension such that when
the plates are superimposed they form a symmetrical coalescing
chamber for transforming fine droplets of carbon dioxide into
larger droplets of carbon dioxide which subsequently solidify and
exit out of an ejection port 32 as explained in detail
hereinafter.
The bottom plate 14 is also provided with another transverse groove
26 which is rearward of the groove 30 and aligned with a hole 33 in
the top plate 12 to provide a passageway for the flow of the fluid
carbon dioxide from the source to the groove 26. In the preferred
embodiment shown in FIG. 5A, the top plate does not have a groove
complimentary to the groove 26. When the flat bottom surface 13 of
the top plate 12 is superimposed over the groove 26 of the bottom
plate 14 there is formed an asymmetrical carbon dioxide fluid
receiving chamber.
An alternative embodiment is shown in FIGURE 5B wherein the top
plate is provided with a transverse groove 24 which is
complimentary in shape to the groove 26 in the bottom plate 14.
When the respective plates 12, 14 are superimposed, grooves 24 and
26 from a symmetrial carbon dioxide fluid receiving chamber.
A symmetrical coalescing chamber is preferred in order to achieve
maximum uniform distribution of the solid particles of carbon
dioxide as they are formed in the chamber and evacuated through the
ejection port 32. On the other hand, the fluid receiving chamber
need not be symmetrical since the incoming fluid is inherently
evenly distributed. It is preferred to form the top plate without
the groove 24 in order to minimize manufacturing costs.
Interposed between the plates 12 and 14 is a film like member 34
which provides a fixed means of metering the carbon dioxide mixture
from the first chamber to the second chamber.
As shown best in FIG. 4, the film-like member 34 includes opposed
arms 36 and 38 which run along opposed sides of the plates 12 and
14. There is also provided at least two projections or fingers 40.
Adjacent fingers 40 are separated from each other by a distance "x"
to thereby define at least one channel 42. One end 44 of the
channel 42 is in flow communication with the first chamber as shown
best in FIGS. 5A and 5B and the other end 46 is in flow
communication with the second chamber to thereby provide a
passageway for the flow of carbon dioxide from the first to the
second chamber. The film-like member 34 is also provided with an
opening 35 which mates with the hole 10 to provide a continuous
passageway for the flow of the fluid carbon dioxide from the source
to the first chamber.
The respective forward portions 48 and 50 of the superimposed
plates 12, 14 define an orifice 52 in which the larger droplets of
carbon dioxide expand and form solid particles prior to exiting
through the ejection port 32.
The ejection port 32 includes opposed walls 54, 56 shown best in
FIG. 6 which diverge or taper outwardly in a manner which enables
the solid/gas mixture to flow outwardly therefrom at a sufficient
speed and force to remove small particles from the substrate
without damaging the substrate.
As shown in FIG. 7, the transverse groove 26 may be provided with
an enlarged area or reservoir 58 which is aligned with and of the
same cross-sectional area as the hole 10 of the receiving assembly
4. This embodiment enables a larger volume of fluid to be supplied
to the first chamber than the specific embodiment shown in FIG.
4.
The source of carbon dioxide utilized in this invention is a fluid
source which is stored at a temperature and pressure above what is
known as the "triple point" which is that point where either a
liquid or a gas will turn to a solid upon removal of heat. It will
be appreciated that, unless the fluid carbon dioxide is above the
triple point, it will not pass the orifice of the apparatus of this
invention.
The source of carbon dioxide contemplated herein is in a fluid
state, i.e. liquid, gaseous or a mixture thereof, at a pressure of
at least the freezing point pressure, or about 65 psia and,
preferably, at least about 300 psia. The fluid carbon dioxide must
be under sufficient pressure to control the flow through the first
chamber and into the second chamber formed by grooves 28 and 30.
Typically, the fluid carbon dioxide is stored at ambient
temperature at a pressure of from about 300 to 1000 psia,
preferably at about 750 psia. It is necessary that the enthalpy of
the fluid carbon dioxide feed stream under the above pressures be
below about 135 BTU per pound, based on an enthalpy of zero at 150
psia for a saturated liquid. The enthalpy requirement is essential
regardless of whether the fluid carbon dioxide is in a liquid,
gaseous or, more commonly, a mixture, which typically is
predominantly liquid. If the subject apparatus is formed of a
suitable metal, such as steel or tungsten carbide, the enthalpy of
the store fluid carbon dioxide can be from about 20 to 135 BTU/lb.
In the event the subject apparatus is constructed of a resinous
material such as, for example, high-impact polypropylene, the
enthalpy can be from about 110 to 135 BTU/lb. These values hold
true regardless of the ratio of liquid and gas in the fluid carbon
dioxide source.
The film like member 34 has at least one channel 42, preferably at
least two channels and most preferably the number of channels
selected is dependent on the width of the channels. That is, the
total width of the channels (i.e. the sum of the distances "x")
must be at least about 10% of the total width of the ejection port
32 as shown in FIG. 1 as the distance "y". The preferred total
channel width is in the range of from about 10 to 20% of the width
of the ejection port 32.
The selection of the number of channels is in part determined by
manufacturing considerations in that the greater the number of
fingers 40, the greater the likelihood that the thin fingers will
not lie perfectly flat in the assembled apparatus. On the other
hand, the lower the number of channels, the less control over the
distribution of the carbon dioxide as it passes from the first to
the second chamber.
The thickness of the film like member 34 is likewise dependent on
manufacturing considerations as well as flow control. For practical
purposes, it is difficult to manufacture the film below 0.001".
While there is no particularly desirable upper range, about 0.001
to 0.020" has been found to be a suitable thickness for the film
34. It is also desirable to make the film 34 of a flexible material
to insure flat face-to-face contact with the plate surfaces when
the plates are secured to each other.
The transverse grooves 26, 28 and 30 and, optionally 24, are
preferably equidimensional having a length and cross-sectional area
dependent on the like dimensions of the ejection port 32. The
length of the grooves 28 and 30 is about equal to the width of the
ejection port 32. The length of the transverse grooves 24 and 26 is
at least sufficient to reach the outermost channels 42. The
cross-sectional area of the chambers should be sufficient to
maintain the pressure in the second chamber in the range of from
about 80 to 160 psia, preferably about 100 psia.
In operation, the fluid carbon dioxide exits a storage tank or
other source of carbon dioxide and proceeds through the connecting
means 6 to the receiving assembly 4 and flows through the hole 10,
the corresponding hole 35 in the film-like member 34 and the hole
33 in the top plate 12 where it then enters the chamber formed by
groove 26 alone or optionally by grooves 24 and 26. The fluid
carbon dioxide then flows out of the first chamber through the ends
44 of the channels 42 formed by fingers 40.
As the fluid carbon dioxide flows out of the first chamber it
expands along a constant enthalpy line to about 80-100 psia as it
enters the coalescing chamber formed by grooves 28 and 30. As a
result, a portion of the fluid carbon dioxide is converted to fine
droplets. It will be appreciated that the state of the fluid carbon
dioxide feed will determine the degree of change that takes place
in the coalescing chamber, e.g. saturated gas or pure liquid carbon
dioxide in the source container will undergo a proportionately
greater change than liquid/gas mixtures. The equilibrium
temperature in the second chamber is typically about -57.degree. F.
and, if the source is room temperature liquid carbon dioxide, the
carbon dioxide in second chamber is formed into a mixture of about
50% fine liquid droplets and 50% carbon dioxide vapor.
The fine liquid droplet/gas mixture continues to flow through the
second chamber. As a result of additional exposure to the pressure
drop, the fine liquid droplets coalesce into larger liquid
droplets. The larger liquid droplets/gas mixture forms into a
solid/gas mixture as the feed proceeds through the orifice 52 and
out the ejection port 32.
Walls 54, 56 forming the ejection port 32 are suitably tapered at
an angle of divergence of about 4.degree. to 8.degree., preferably
about 6.degree.. If the angle of divergence is too great (i.e.
above about 15.degree.), the intensity of the stream of solid/gas
carbon dioxide will be reduced below that which is necessary to
clean most substrates.
The second chamber serves to coalesce the fine liquid droplets into
larger liquid droplets. The larger liquid droplets form minute,
solid carbon dioxide particles as the carbon dioxide expands and
exits toward the substrate at the ejection port 32. In accordance
with the present invention, the solid/gaseous carbon dioxide having
the requisite enthalpy as described above, is subjected to desired
pressure drops from the first chamber through the channels 42 into
the second chamber, the orifice 52 and ejection port 32.
Although the present embodiments incorporate two stages of
expansion, those skilled in the art will recognize that nozzles
having three or more stages of expansion may also be used, with
three or more sets of transverse grooves.
Pure carbon dioxide may be acceptable for many applications using
the present invention, for example, in the field of optics,
including the cleaning of telescope mirrors. For certain
applications, however, ultrapure carbon dioxide (99.99% or higher)
may be required, it being understood that purity is to be
interpreted with respect to undesirable compounds for a particular
application. For example, mercaptans may be on the list of
impurities for a given application whereas nitrogen may be present.
Applications that require ultrapure carbon dioxide include the
cleaning of silicon wafers for semiconductor fabrication, disc
drives, hybrid circuit assemblies and compact discs.
For applications requiring ultrapure carbon dioxide, it has been
found that usual nozzle materials are unsatisfactory due to the
generation of particulate contamination. Specifically, stainless
steel may generate particles of steel, and nickel coated brass may
generate nickel. To eliminate undesirable particle generation in
the area of the orifices, the following materials are preferred:
sapphire, fused silica, quartz, tungsten carbide, and
poly(tetrafluoroethylene). The subject nozzle may consist entirely
of these materials or may have a coating thereof.
The invention can effectively remove particles, hydrocarbon films
particles embedded in oil and fingerprints. Applications include,
but are not limited to the cleaning of optical apparatus, space
craft, semiconductor wafers, and equipment for contaminant-free
manufacturing processes.
EXAMPLE
A cylinder of Airco Spectra Clean carbon dioxide equipped for
liquid withdrawal was connected via a four foot length of 1/8 inch
O.D. stainless steel tubing to the inlet fitting of a nozzle of the
type shown in FIGS. 4 and 5A. The nozzle was made of Type 316
stainless steel having an overall width of 21/2 inches and an
outlet aperture of 2 inches.
The distance between the first chamber and the second chamber (i.e.
the length of the metering channels 42) was 5/8 inch. The length of
the second orifice extending from the coalescing chamber to the
beginning of the divergent walls 54, 56 of the ejection port 32 was
9/16 inch. The walls 54, 56 were tapered at angle 6.degree. thereby
providing an expansion ratio of 4:1.
The film-like elements employed in the respective nozzles each had
a thickness of 0.001 inch and included four metering channels 42.
The channels 42 of the respective film-like members 34 were 0.40,
0.60 and 0.80 inch, respectively.
The substrate to be cleaned was a silicon wafer which was
artificially contaminated with zinc sulfide powder dispersed in
ethyl alcohol.
The nozzle was operated in free air for about 5 seconds to cool
down and establish stable flow of the product mixture. Then the
nozzle was moved to a position of 45.degree. with respect the
substrate surface at a distance of about 3/4 inch.
Liquid carbon dioxide from the cylinder was supplied to the nozzle
at a pressure of 850 psia. The 0.040 inch wide nozzle produced a
flow rate of only 2 scfm and a coalescing chamber pressure of less
than 80 psia. As a result, the solid carbon dioxide particles
produced were too big and moved at too slow a velocity to remove
the zinc sulfide particles from the substrate.
Both the 0.060 and 0.080 inch wide nozzles were effective in
removing the contaminated particles as they produced a smooth
stable flow of solid carbon dioxide particles at a flow rate of 3.4
scfm and 4.7 scfm, respectively. The substrate was examined under
ultraviolet light which causes the contaminants to fluoresce. No
trace of the contaminants was present on the substrates.
While the present invention has been particularly described in
terms of specific embodiments thereof, it will be understood that
numerous variations of the invention are within the skill in the
art, which variations are yet within the instant teachings. For
example, radial inflow or outflow nozzles may be constructed to
respectively clean the outside or inside surfaces of tubular
structure nozzles having conical inflow and outflow passages may be
constructed for the same purpose. Accordingly, the present
invention is to be broadly construed and limited only by the scope
and the spirit of the claims appended hereto.
* * * * *